<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            border: 1px solid black;
        }
        .box1{
            float: left;
            width: 200px;
            height: 200px;
            background-color: pink;
            margin-right: 10px;
        }
        
        /* 11111 */
        /* .box::before,.box::after{
            content: "";
            display: table;
        }
        .box::after{
            clear: both;
        }
        .box{
            zoom: 1;
        } */

        /* 222222 */
        /* .box::after{
            content: "";
            display: block;
            height: 0;
            clear: both;
            visibility: hidden;
        }
        .box{
            zoom: 1;
        } */

        /* 333333 */
        .box2{
            clear: both;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="box1"></div>
        <div class="box1"></div>
        <div class="box1"></div>
        <div class="box1"></div>
        <div class="box1"></div>
        <div class="box2"></div>

    </div>
</body>
</html>